x and y are rectangular co-ordinates of any point as pint curve, B the centre being the origin for presented by a, and p be made equal to a 2, the prod two lines as Pp, P'p (not drawn in the figure) will be to a. But, in order to allow BP to be constant for different curves, the equation may be put in the form (x2 + y2)2+a2 (a2-b2)-2(-3)=0, in which b may be of any magnitude whatever from zero infinity; and from this equation the value of the rectang Pp, P'p for any one curve is the product ab. In explaining the phenomena of polarized rings on the un latory hypothesis, it is assumed that a pencil of polarized in its passage along the axis, or along one of the axes of a do refracting crystal, ceases to have its ordinary and extraord ray polarized in planes exactly at right angles to one an in consequence of the different degrees of retardation the waves in the two kinds of rays experience in phases: hence, instead of the dark spot which, on through the crystal, so that they emerge from it in dif into the plate PQ (Fig. 1), when the planes SAB ABC are at right angles to one another, would present its the eye, the light partially depolarized gives rise, on en the eye, to the perception of the coloured rings. The crystal being uni-axal, let v be the velocity of before it is incident on the crystal, A the length of and the expression for the intensity of the impres light when the vibration is a maximum: also within 2 ubin ozude arab grad crystal, let a sin. vt be the extent of a vibration of ized light (perpendicularly to the primitive plane of palm tion) in the ordinary ray; and, representing the ex the retardation of the extraordinary ray above that of other by R, the vibration of a particle perpendicular to plane of primitive polarization, in the most retarded be represented by a sin, 2 (vt+R), ndi vadida a onborg ronsyor bolon (5) has (8) anoisery By two successive resolutions of forces, the vibration pendicular to the plane of primitive polarization reduced to directions perpendicular and parallel to a plane through the optic axes of the crystal (the angle between planes being represented by 0), and then to directions pendicular to the plane of polarization at the analyzing (those vibrations alone producing a perception of light eye, which are perpendicular to the plane of polari the angle between that plane of polarization and the p primitive polarization being represented by a; a resu bration, for the ordinary pencil produced by the refraction of the crystal becomes a cos. O cos. (0+a) sin, et of Sputnik cable of bar aille de When a plane passing through AB (Fig. 1), and the two and, for the extraordinary pencil, ond en hal optic axes of the crystal is made, by turning the plate of crystal on the ray AB, to coincide with the plane SAB of primitive polarization, the dark curves passing through the two polar points P and P' (Fig. 4) become one straight line MN; the coloured rings come together as in the figure and Developing sin. 2(vt+R) and then adding together on whion bas 22 0002 squares of the coefficients of sin. - et and cos. ut the odt diiw is, by the undulatory theory, an expression for the inte of light in the image, at a point where the apparent field view is intersected by a ray whose inclination to the axis (Fig. 1) enters into the expression for R; the plane pas through such ray and the axis AB making with the plan analyzation a variable angle equal to e+a. Putting for a the above expression has the form cos. a-sin. (24-2) sin. 24 sin. R and, when a 90°, or the planes of polarization for the AB and BC are perpendicular to one another, the last pression becomes Treig past a tit Jodish bune din don disa sin. 24 sin. R the length A of a wave differs for the different kinds of but the conclusion arrived at being independent of any ticular value of A, it follows that all the light vanishes w in which p is equal to half the axis mn of the particular curve, 40, 90°, 180° and 270°; consequently there are at the s rich when =0, 90°, 180°, and 270° becomes a2, a naxiim: hence the coloured field of view will be traversed by a me cross whose arms are at right angles to one another. I have other values, the expression (b) or the density of will vanish when R=0, RA, R=2A, &c. But the alent of R containing, as a multiplier, sin. i; (i being incidence of a ray on the crystal after diverging from A; the angle which, as above mentioned, a ray from A makes the axis AB) one giving successively to R the values 0, , &c., it is found that sin. i has corresponding values pro 21 6x T' T' T' tional to 0, V, W, , &c.; (T being the kness of the plate of crystal) and since the expression (b) the same value, and vanishes or is a maximum, for all rays se angles i of incidence in the conical pencil diverging Aare the same, it follows that, about the axis of the field ew, there are dark rings whose radii have the proportions ¥2, x/4, 'x^6, &c. The expression (b) is a maximum x, &c., or when sin. i has values pro R 1 3 5 λ 3λ T' innal to √ √ √, &c.; and it follows that, t the axis of the field, there is a series of bright rings se radii have the proportions of √1, √3, No5, &c. he expressions (b) and (c) added together produce a2; the tints of the several rings formed when the planes of ization in AB and AC are coincident are complementary which are formed when those planes are perpendicular another and in the former case the bright rings have which are proportional to No2, 4, 6, &c., while the rings have radii proportional to /1, No3, No5, &c. the investigation of the phenomena of the rings seen Fig. 4) when IK is a bi-axal crystal having its surfaces perpendicularly to the plane passing through the axis; also for the phenomena presented when a plate of crystal, axal or bi-axal, is so cut that the surfaces are not perpenlar to the axis, or to the plane passing through the two see Airy's Tracts (Undulatory Theory). The reader sferred also to Sir David Brewster's Treatise on Optics in Edinburgh Encyclopædia, and to Sir John Herschel's tise on Light in the Encyclopaedia Metropolitana. OLEMONIUM (#оλeμάvioν of Dioscorides), a genus of its, the type of the natural order Polemoniacea. It has a panulate 5-cleft calyx, a rotate corolla, and a short tube a 5-lobed equal erect limb: 5 equal stamens inserted in throat of the corolla with filaments dilated at the base, rded in a continuous ring, and nearly closing the throat, Jincumbent anthers; a roundish capsule with membranous staceous valves, covered with the permanent calyx and ay-seeded cells; the seeds oblong, trigonal, and filled with emen; the radicle twice as long as the cotyledons. The gies are crect herbaceous plants, with alternate unequally nate leaves; the flowers terminal, bracteated, arranged on cled corymbs, with blue or white corollas. About twelve cies have been described, most of them being cultivated known in our gardens as Greek Valerian. P. caruleum, common Greek Valerian, Jacob's Ladder, Ladder of Heaven, has a glabrous stem, pinnate leaves, ovate ccolate acuminated leaflets, the segments of the calyx gure or elliptic, lanceolate, pointed; the panicle downy, andalar. The stem is one or two feet high, the leaves alraste, the flowers numerous, bright blue or white, somewhat ircoping. It is a native of Europe and America, and is und in Great Britain, but is a rare plant. A great number varieties have been described. It is a favourite plant in gardens, and will grow in any common garden soil, and aay be readily propagated by dividing the root or by seed. though deriving its generic name from the Polemonium of Dioscorides, it does not appear to agree at all with his description of that plant, and Fraas refers it to Hypericum olympicum. Great virtues were attributed to the antient Polemonium, and these were transferred to the modern plant; but neither the antient nor modern plant possesses any active medical properties. Slight astringency is the only property possessed by any of the species of Polemonium. (Fraas, Synopsis Plant. Flora Classica; Don, Gardener's Dictionary; Babington, Manual of Brit. Bot.) POLICE. In Scotland the larger towns have separate police statutes, by which the management and control of the system is put into the hands of elected commissioners. The act 3 & 4 Wm. IV. c. 46, is a general police act, the provisions of which, or a portion of them, may be adopted, so as to become law, by any royal burgh, burgh of regality, or burgh of barony, at a meeting of a specified number of tenpound householders. The act provides for the election of commissioners with power of management and control, by the same class of persons who are entitled to decide on the adoption of the act. By 2 & 3 Vict. c. 65, called the Rural Police Act, the commissioners of supply of any county are authorised, at a meeting called on requisition by ten of their number, to assess the county for maintaining a constabulary force. The act directs the commissioners to publish annual accounts of receipt and expenditure. The system is for rural police purposes, called the 'Rogue Money.' co-operative with the expenditure of an old established fund POLLA JUOLI, PIERO and ANTONIO, two distinguished Florentine painters and sculptors of the fifteenth century; they were the sons of Jacopo del Pollajuolo. Piero was the pupil of Andrea del Castagno; Antonio was the more distinguished, he was the pupil of Lorenzo Ghiberti, and assisted him in the celebrated gates of the baptistery of San Giovanni; he became also a famous goldsmith, and was as such without a superior in Florence; Maso Finiguerra was his contemporary. The two brothers generally executed their paintings together; the best of them, says Vasari, is the Martyrdom of St. Sebastian, painted in 1475, in the church de' Servi at Florence. St. Sebastian was painted from nature and is one of the best figures that had been painted up to that time; it is engraved in the Etruria Pittrice of Lastri. Antonio is said to have been the first artist who studied the dead subject for the purposes of design. Antonio Pollajuolo was invited to Rome in 1484, after the death of Sixtus IV., by Innocent VIII., and he made the monuments of Sixtus IV. and of Innocent VIII.; that of Sixtus, in 1493, is now in the chapel of the Sacrament in St. Peter's; the monument of Innocent is also in St. Peter's. Antonio was also a medalist, and he engraved three or four plates, which are extremely scarce. (Vasari, Vite de' Pittori, &c., and the notes to Schorn's German translation; Rumohr, Italienische Forschungen Cicognara, Storia della Scultura; Baldinucci, Notizie dei Professori del Disegno, &c.) POLLAJUOLO, SIMÓNE DEL, or Simon Masi, a distinguished architect, commonly called Il Cronaca, from his ability in relating stories, was born at Florence in 1454. He was related to Antonio del Pollajuolo, and lived with him some time at Rome. He is chiefly distinguished for the Palazzo Strozzi, one of the most solid and imposing buildings of Florence; it was commenced in 1489 by Benedetto da Maiano, but was completed by Cronaca, and the great cornice or entablature and the court in the interior are from the designs of Cronaca. The ironwork and the beautiful lanterns are by Niccolo Grosso, commonly called Caparra, a nickname which was given to him by Lorenzo de' Medici on account of his always persisting in being paid before he delivered his work; Caparra signifies deposit or advance-money. Grosso was the most celebrated smith of his time. Cronaca built also the great council-hall for the Signoria of Florence, which was afterwards enlarged and embellished by Vasari; the church of San Miniato al Monte, the convent Dei Servi, and the Sacristy of Santo Spirito. He was a follower of Savonarola: he died in 1509. (Vasari, Vite de' Pittori, &c.; Gage, Carteggio Inedito d'Artisti.) POLLOK, ROBERT, a poct and miscellaneous writer, was born at Muirhouse, in the parish of Eglesham, in Renfrewshire, in 1799. He studied at the university of Glasgow, and afterwards followed the course of theological education necessary to fit him for a charge in the United Secession Church, of which he became a licentiate in 1827. His principal work, which is in some respects auto-biographical, speaks of the solitude and pastoral simplicity of the scenes in which he passed his youth In rural quietude, 'mong hills and streams And there, watching his little flock, or heard He was a hard student, and appears to have been early endowed with a strong ambition to create for himself a permanent name in literature. In his own words The ancient page he turned, read much, thought much, Just before he received his licence, he had finished the poem on which his literary reputation rests, The Course of Time. A work so ambitious, from the hands of a country student attached to a small body of dissenters, was not likely to find a patron among publishers. It happened to be shown to Professor Wilson, of Edinburgh, as a curiosity, and he was astonished to discover in it great poetic power. In deference to his recommendation it was published by Mr. Blackwood, of Edinburgh, and speedily passed through several editions. Its flight of genius was a novelty in the class of evangelical religious literature to which it belonged, and besides pleasing those who are partial to that class of religious literature, it was a boon to many who are inclined to read religious books, but are repulsed by their general dryness and insipidity, while it was warmly admired by the literary world at large. Mr. Pollok's partial admirers expected for him a place on a level with Milton. After the novelty of such a phenomenon had however passed off, the book became neglected by purely literary readers; and at this day it may be said that it is estimated too highly by the religious, and too insignificantly by the literary world. It is a work of great power, but meagre fancy. It has a considerable amount of sentiment deeply tinged with religious asceticism. Many sentiments are spun out or repeated, and the interest frequently flags. The work exhibits a great command of the English language and a power of terse rapid melodious diction. Pollok's mind was evidently imbued with 'Paradise Lost,' and he follows Milton often to the verge of slavish imitation. | Before the publication of his poem this interesting young man had undermined his constitution by excessive mental labour, and he scarcely lived to see its success. On the recommendation and through the assistance of his friends he was preparing for a journey to Italy. The simplicity in which his family was brought up, may be imagined from the circumstance that his sister, who was to accompany him, obtained a certificate of good character from the minister and elders of her parish, believing that such a testimonial was all the more necessary as they were about to proceed to the land of graven images.' The disease had however made too great progress to admit of his leaving Britain, and he died near Southampton on 15th September, 1827. POLYCARPON (from woλú, many, and kúpos, a seed or fruit seeds numerous), a genus of plants belonging to the natural order Paronychieæ. The sepals are slightly cohering at the base, the petals 5 and emarginate. The stamens from 3 to 5; styles short and 3 in number. The fruit is 1celled, 3-valved, and many-seeded capsule. P. tetraphyllum has triandrous leaves, emarginate petals, the stem-leaves in fours, and the leaves on the branches opposite. In young plants the leaves are often all opposite. It is a native of the coasts of the south-west of England, of Europe, and the Canary Islands. There are two other species of Polycarpon: P. alsinefolium, an inhabitant of Europe, the Cape of Good Hope, and Holland; and P. peploides, a native of Sicily and France. The seeds of the annual species require only to be sown in the open border in spring. The last species, being perennial, should be grown in a small pot, and placed among other alpine plants. (Don's Gardener's Dictionary; Babington's Manual of British Botany.) | mens half as long again as the perianth, the nut triquetrom its faces ovate, smooth. The calyx is rose-coloured deeply five-cleft, obtuse, and spreading. The fruit is and shining. This plant is one of the most powerful vegy table astringents, its root contains tannin and gallic acid abundance; a decoction of it is employed in gleet and corrhoea as an injection, as a gargle in sore-throats, ani lotion to ulcers attended with excessive discharge. Inter it has been used combined with gentian in intermittents may also be employed in passive hæmorrhages and diar: P. amphibium has a dense ovate cylindrical spike sta ovate oblong floating leaves, a compressed smooth shining 5 stamens, and a creeping root. The flowers are of a r crimson colour. It is a native of England in ponds, d and wet places. It is a fine showy plant, but one of most difficult to eradicate from lands recovered from rivers drained lakes and marshes. The subaquatic stems ro every joint, and extend to a surprising length, rising th the soil. They bear some resemblance to sarsaparilla according to Coste and Willemet they are substituted i drug by the herbalists of Nancy; these authors also that the apothecaries and druggists of Lorraine giver preference. P. hydropiper, the Water-Pepper, has drooping filia terrupted spikes, lanceolate wavy leaves, glandular peri a large compressed nut, its faces ovate, acute, and of apara black colour. It is a hot acrid plant, and is reputed powerful diuretic, but it loses its activity by drying therefore requires to be used in a fresh state. It de of a yellow colour. The seeds, according to Bulliard, area in some of the French provinces instead of pepper. leaves are so acrid as to act as vesicants. It is a England in ditches and wet places. P. aviculare has from one to three flowers together, lanceolate leaves, or elliptical plane stalked lanceolate =) ocreæ, with few distant simple nerves at length by growa coming torn, a triquetrous nut with raised points shorter the perianth. Its numerous seeds supply abundant food birds; they are said to be emetic and cathartic. Than that in Japan a blue dye is prepared from this plant. T many other species of Polygonum, natives of Great Bra other parts of the world, but too numerous for descripti P. tinctorium is cultivated in France and Flanders on a of the fine blue dye extracted from it. The sets barbatum are used in medicine by the Hindu practi and are said to ease the pain of griping in the co leaves of P. hispidum are said by Humboldt to be subs in South America for tobacco; and P. anti-hæmorrh esteemed in Brazil on account of its astringency i poultices, &c. &c. The juice, as well an infusion of the - A when burned, is employed by the Brazilians in the taltion of syrup and the condensation of sugar. P. Fagopyrum, the Buck-wheat, is now referred to Fe rum esculentum. [FAGOPYRUM, P. C. S.] (Lindley's Vegetable Kingdom; Babington's Man Bot.; Burnett's Outlines of Botany; Lindley's Medica.) POLYPO'DIUM. [FILICES, P. C. S.] DIUM. POLYPO'GON (from woλú, and wúrywv, a beard), a ra of grasses belonging to the tribe Agrostideæ. It has s nearly equal glumes, each furnished with a long s just below the emarginate summit. The palle are than the glumes, the outer ones usually curved from the summit. P. monspeliensis has the setæ more than twice as the rather obtuse glumes. It has a fibrous root, a st a foot to foot and a half high, a dense lobed silky often two inches long. The glumes are linear and It is a very beautiful grass, and is a native of Great Br salt marshes. It is the ἀλωπέκουρος (fox-tail) of To phrastus, Hist. Plant. 7, 17. lanceolate. It is a British species and is found in m salt marshes. P. littoralis has its sete equalling the acute glumes. POLYGONUM (the Greek Toxuyovov, much-produc- root is somewhat creeping, the stem about a foot high, live'), a genus of plants belonging to the natural order Poly-panicle close lobed and purplish. The glumes are gone. It has a 5 parted perianth, from 5 to 8 stamens, and from 2 to 3 styles; a 1-seeded trigonous or compressed nut, lateral incurved embryo, the cotyledons not contorted. This is a very extensive genus, containing the knotgrasses, bistorts, persicarias, and buckwheats of our own waysides, fields, and gardens. They grow in almost any soil, some being aquatic, and others flourishing in sandy sterile tracts. P. Bistorta, Snake-weed, has a dense spike, ovate subcordate leaves, the radical leaves with winged foot-stalks, the sta (Babington's Manual of British Botany.) POLYTECHNIC SCHOOL. This Institution, v has produced so many men eminent for their stan in pure and physical science, originated, at the time great revolution in France, with one of the represetil the people, named Prieur (de la Côte d'Or), who t member of the Committee of Public Safety, and charges ► dr. e duty of superintending the practice of the arts which | was the origin of an institution of which, with re- the course of the same year, 1795, the National Conon decreed that the Ecole centrale des Travaux publics' ald take the name of 'Ecole Polytechnique,' and some regulations were made concerning the subjects in which feandidates for admission were to be examined. In matheBes there was required a knowledge of algebra, as far as Fresolution of equations of the four first degrees, with its iration to geometry; the summation of series; trigonotry and the properties of conic sections. For the conence of persons residing in the provinces, the examinafor admission to the school were appointed to be held, the same time, at towns situated in different parts of nce; the municipal authorities of the towns were to be sent, and the examinations were to be conducted by y qualified persons who were to attend for the purpose. outh between 16 and 20 years of age only was admissible; before a candidate was allowed to present himself for exination, he was required to exhibit a certificate of good luct, and of his attachment to republican principles; or, the sentiment was sometimes expressed, his love of liberty bed equality, and hatred of tyrants. A successful candidate was required to report himself to the chiefs of the institution in Paris, on an appointed day: an allowance of money equal to that which was made to a private artillery-man of the first class bring assigned to him for his travelling expenses; and, during the time that he remained at the school, the pupil was to repay 1200 livres (501.) yearly. Three years were hered as the time necessary for the completion of the anted course of study; and a student was not, under any circumstances, to remain at the school longer than four years. Public examinations were to take place at the end of each year; and pupils who should not be found to have attained the requisite proficiency in at least three-fourths of the subjects constituting the prescribed course of education were to be withdrawn from the institution. In the following year (1796) the National Convention decreed the formation of eight special schools for instruction in matters concerning the different professions which relate to the public service; these were the Ecole d'artillerie at Châlons; des ingénieurs militaires at Metz; des ponts et chaussées, des mines, des géographes, des ingénieurs de vaisseaux, de navigation, and de marine, at Paris and the students in all these institutions were to receive salaries from the state. A student desirous of serving the country in any one of the professions for which the special schools were appointed, might, after being two years at the Polytechnic School, become a candidate for that particular profession; and if, after examination, he was found qualified, he was either admitted in the special school or was, on a vacancy occurring, appointed immediately to a post in the department to which he aspired. An unsuccessful candidate might remain at the Polytechnic School during the third year; and, at its expiration, he might again present himself as a candidate for examination. A student admitted to exercise the functions relating to any particular department of the service was also allowed to remain during the third year at the Polytechnic School, in order that he might complete the course of study at that institution. The government of the school was placed under the direction of the minister of the interior; and it was the duty of that minister, under the Executive Directory, to assure himself that the regulations were carried into effect: the number of students was, at the same time, reduced to 360. At the end of the first year, 40 young men were taken from the school to serve as officers of engineers; and these performed duty in Paris till their services were required with the armies in the field: nine were admitted to the school for military engineers and several were appointed to posts in the other special schools. The necessity of having teachers for the purpose of preparing the junior pupils, or such as required more detailed instruction than could be afforded by the professors, led, in 1796, to the appointment of assistant preceptors; and these were selected from among the students who, having completed their course of education, were qualified to perform that duty at the same time, also, the students were inade to wear a military uniform. It is remarked that Bonaparte, after his return from the campaigns in Italy, often visited the institution, where he took pleasure in encouraging the youths to prosecute their studies; and when he sailed on the expedi tion to Egypt he took with him twenty of the most advanced pupils: he was also accompanied, in that expedition, by Monge, who was the principal professor. In the year 1800 the school was re-formed and the number of students was reduced to 300: the mathematical course was increased; and it was decreed that candidates who had served in the armies of the republic during three years should be admissible till they were 26 years of age. The pupils, in general, had then the rank of serjeants of artillery, and their daily pay was 98 centimes (9 pence). The military uniform was continued, and on the margin of the buttons were the words Ecole polytechnique:' some alterations were made in the mode of conducting the examinations; and a council was appointed for the purpose of attending to the state of the school, and also of suggesting measures for its improvement. When Bonaparte became emperor, in 1804, the school was again remodelled, and Monge was replaced at its head: it then acquired the title of Ecole polytechnique impériale, and it received an organization completely military. While that extraordinary man governed France the institution may be said to have been in its most flourishing state; and the subjects of the course of study were then arranged under thirteen heads, as follow:-Mathematical analysis; mathematical analysis applied to geometry descriptive geometry; mechanics; machinery; natural philosophy; chemistry; geodesy; topography; the military art; architecture; drawing of figures and landscapes; grammar and the belles-lettres. that time also, the following were the subjects a knowled of which was required for admission to the school;-1. Arit metic, with an explanation of the metrical system. 2. Al containing the resolution of equations of the two first indeterminate equations of the first degree-the mes 4 At 1. Crataegus (kpáraiyos). Calyx urceolate, 3-c petals orbicular; ovary 2-5-celled; styles 2-5, gla' the fruit fleshy, ovate, containing a bony putamen. [L TEGUS, P. C.J tion of equations-demonstration of the binomial theorem-PO'MEÆ, a section or sub-order of the natural orde the method of commensurable divisors, and that of equal Rosacea. [ROSACE, P. C.] The following is a syropi roots the resolution of numerical equations by approxima- the genera belonging to this section of plants: tion-and the elimination of unknown quantities in equations of any degree having two unknown quantities. 3. The theory of proportion-progressions and logarithms. 4. Elementary geometry and plane trigonometry. 5. Part of the course of descriptive geometry. 6. Discussion of lines represented by equations of the first and second degrees with two unknown quantities-the principal properties of conic sections. 7. Statics demonstrated synthetically and applied to the equilibrium of simple machines, as the lever, wheel and axle, &c. 8. The candidates were also required to translate part of a Latin author in prose, and give a grammatical analysis of French phrases. 9. To construct, with scale and compasses, any geometrical figure which the examiner might indicate. And 10. To draw and shade, with pencil, a figure from a given model. 2. Raphiolepis (from papis, a needle, and Aeric, a The limb of the calyx funnel-shaped, deciduous; the o 2-celled, 2-styled; the fruit with a thickened closed disk, a papery putamen containing 2 gibbous seeds, 3. Chamamelis (from xauai, the ground, and apple). Calyx truncate, with 5 little teeth; the petals crose; the stamens 10-15; the ovary 1-celled; the single; ovules 2, erect. 4. Photinia (from pwrtwig, shining). Calyx 5-treb petals reflexed; ovary villous, 2-celled; styles 2, glake fruit 2-celled inclosed in the fleshy calyx. 5. Eriobotrya (from ptor, wool, and Bórpus, m Calyx woolly, 5-toothed; petals bearded; styles 5, inclosed; fruit closed, 3-5-celled. 6. Cotoneaster. Flowers polygamous; calyx t bluntly 5-toothed; petals short; stamens length of the cine teeth; styles glabrous, shorter than the stame carpels, parietal, inclosed in the calyx with 2 ovules. C NEASTER, In 1814 the students of the school took a share in the defence of Paris, and even assisted in serving the guns directed against the allies. On the restoration of the Bourbon family, the school was for a time suppressed; but it was afterwards revived, and it then received the title of Ecole Royale Polytechnique, which it still retains. Occasionally since, unmindful of the submission due to the government which educates them, the students have, as in 1816 and 1830, manifested dispositions to put themselves in opposition to its measures: the acts of insubordination which took place in 1845 appear to have originated merely in a dislike which, for some reason, the students entertained to a person who had been appointed one of the examiners; but those acts were so violent that the king, Louis-Philippe, entirely suppressed the 8. Mespilus. Calyx 5-cleft; segments foliaceous institution. It has, however, again been revived, and, except nearly orbicular; disk large, filled with honey; styles a few of the most culpable, the same students have been re-glabrous; fruit turbinate, open at the apex, 5-celled; admitted. Calyx 5-cleft; petals lanceolate: st rather shorter than the calyx; ovary of 10 cells or 5 b ones with a solitary ovule in cach partition; styles 5, at the base; fruit 3-5-celled; seeds 3-5; the endocar tilaginous. carp bony. [MESPILUS, P. C. S.T 9. Osteomelis (from darior, a bone, and μnov, an a Calyx 5-cleft; petals oblong; styles exserted, the same. as the stamens, bearded below; ovary 5-celled; cells 1-sa. fruit closed, woolly; endocarp bony. The object of the Polytechnic School is still the same as at its formation; and the young men are educated for the following branches of the public service; viz. l'artillerie de terre et de mer; le génie militaire et le génie maritime; la marine royale et le corps des ingénieurs hydrographes; les ponts et chaussées et les mines; le corps royale d'état-major; styles usually 5, rarely 2 or 3; fruit closed, 5-celled, les poudres et salpêtres, and l'administration, des tabacs. sum. The number of students is now reduced, to 200, and the duration of the course of instruction is two years, Each student subscribes annually 1000 francs (417. 13s. 4d.), and the expense of his clothing is, in addition, about half that The commander-in-chief of the French armies is the head of the institution, and all the students are subject to military law. A candidate for admission must be a native of France, or a naturalized subject of the kingdom, and he must be between sixteen and twenty years of age. Military men are, however, admitted till the age of twenty-five; but they cannot receive leave of absence, to prepare themselves for the examination, till they have been two years with their regiinents. The government does not engage itself to receive in its employ all the young men who have been educated at the school but such as pass their final examination are allowed, according to the degree of merit which is awarded to them by the jury appointed to decide respecting their qualifications, to enter one of the branches of the public service as far as the vacancies will permit. In the gift of the Ministre de la Marine there are four scholarships, in that of the Ministre de l'Intérieur eight, and in that of the Ministre de la Guerre twelve; and these are for the benefit of youths whose parents or guardians are unable to pay the subscription. They are called places gratuites, and each is equivalent to two places demi-gratuites which the minister may grant to persons who are capable of paying half the amount of the subscription. The programme of the subjects, a knowledge of which is required preparatory to admission, is very nearly the same as that which has been given above. The students rise at 5A.M., and breakfast at 74; their hours of study and recreation for each day are regulated, and they dine at 2 P.M. They sup at 8, and at 94 P.M. the lights are extinguished,,! The Journal de l'Ecole Royale Polytechnique' continues to be published by the Conseil d'Instruction,' and it contains many valuable essays on subjects relating to the highest branches of mathematical science. The earlier papers were contributed by La Grange, Monge, La Place, Poisson, Prony, and other celebrated men; and those of more recent date are written by the ablest mathematicians of France, several of whom have been pupils of the institution. 6 10. Pyrus. Calyx urceolate, 5-lobed; petals rec cartilaginous; seeds 2 in each cell. [PYRUS, P. C.] 11. Cydonia, Calyx 5-cleft; petals orbicular; style. fruit closed, 5-celled; cells cartilaginous, many-seeded; covered with pulp. The species of the genus Raphiolepis are known ly name of Indian Hawthorns. They are natives of v parts of Hindustan and China. There are six species (45 genus, four of which have been cultivated in this county, introduced as species of Crataegus or Mespilus. Thes R. Indica, a native of India and China; R. pheostranative of China; R. rubia, a native of Cochin-China, R. salicifolia, a native of China. All the species are tre.. their native climates, with evergreen crenated cora reticulated leaves; flowers in terininal racemes, with na petals, and red stameus, The species will grow we a mixture of sand, loam, and peat. R. Indica, in Britis dens, is an evergreen shrub, flowering from February August, and in many instances has borne our winters for years. It is probable all the species would bear our wal if planted against a south wall, and covered with ne severe weather. The genus Chamamelis was constructed by Lindley single species, C. coriacea, which is found in the isla Madeira. It grows on the sea-cliffs to the east of Func about a mile from the town on the road to Canico. The species of the genus Photinia are evergreen trees # undivided coriaceous serrated or entire leaves, and t in terminal corymbose, panicles, followed by small frunt. I require the same treatment as the species of Cratagus, & are eminently ornamental. เ P. serrulata has oblong acute serrulated leaves, a native of Japan and China, It has been long cultivate Great Britain as a standard in the open air, in warm situ Where it is too cold to grow it as a standard, it may be against a wall. Fit associates for it against a wall are tinia arbutifolia, Crataegus glauca, C. mexicana, Ba indica, and Eriobotrya japonica. (Loudon.) Three species of Photinia, P. arbutifolia, P. integrifolia, P. de have been cultivated in this country. There are s five other species described, natives of Asia, which *. probably be cultivated with success. The species of Eriobotrya are less hardy than the ot |